1. Field of the Invention
The present invention relates to an electroconductive member for electrophotography, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
In an electrophotographic apparatus as an image forming apparatus adopting an electrophotographic system, an electroconductive member is used as a charging member or a transfer member. Such electroconductive member is required to maintain suitable electrical characteristics over a service life of the electrophotographic apparatus.
From the viewpoint of controlling the electrical characteristics of the electroconductive member within a suitable range, an electron conductive agent such as carbon black and an ion conductive agent such as a quaternary ammonium salt have been used for resistance control. However, for example, in the case where the electroconductive member is used as the charging member over a long period of time, even when local resistance unevenness is small, there is a risk in that an electric field is concentrated in the local portion with resistance unevenness to cause abnormal discharge, and consequently, a void image may be generated. Further, when the resistance of the electroconductive member increases with long-term use, discharge (hereinafter sometimes referred to as “downstream discharge”) occurs on a downstream side of an abutment portion between the electroconductive member and the body to be charged, and consequently, a horizontal streak-like image may be generated.
As described above, it is not easy to maintain suitable electrical characteristics over a long period of time. As a method of maintaining the electrical characteristics of the electroconductive member, the following methods are disclosed. Japanese Patent Application Laid-Open No. 2008-276026 discloses a method involving dispersing roughening particles in a surface layer of the charging member so as to form surface irregularities. Further, Japanese Patent Application Laid-Open No. H07-140755 discloses a method involving providing a non-electroconductive two-dimensional mesh on a surface of the charging member.